1. Technical Field
Exemplary embodiments relate to on-die termination, and more particularly to an on-die termination circuit, a data output buffer, a memory device, a memory module, a method of operating the on-die termination circuit, a method of operating the data output buffer, and a method of training on-die termination.
2. Discussion of the Related Art
On-die termination (ODT) is a signal termination circuitry or component used for impedance matching signal lines located inside a semiconductor chip. When signals are transferred between devices via interfacing signal lines, signal reflection can be suppressed if the lines are impedance matched. An ODT can be used, for example, to terminate signals that interface between a memory controller and a memory device. A basic termination device is a termination resistor (RTT) that is matched to an impedance of a transmission line.
A conventional use of an ODT may involve a memory device that receives an ODT signal for enabling an ODT circuit through an ODT pin, and synchronizes the ODT signal with an external clock signal. The memory device turns on the ODT circuit in response to the synchronized ODT signal at a predetermined time, such as a fixed number of clock cycles, after receiving the ODT signal. In such use of the ODT, even when a data strobe signal is not generated, a clock synchronization circuit needs to be turned on to synchronize the ODT signal with the external clock signal. Other usage of ODTs may require a latency circuit for turning on the ODT circuit after a predetermined latency from when the ODT signal is received.